In order to provide good performance and low prices, integration in three-dimensional semiconductor devices has been increased. In semiconductor memory devices, since its degree of integration is an important factor for determining a product's price, its increased integration is beneficial. In two-dimensional or planar semiconductor memory devices, since its degree of integration is mainly determined by an area that a unit memory cell occupies, it is greatly affected by a level of a fine pattern formation technique. However, since expensive equipment is typically required for forming small patterns, although the degree of integration is a two-dimensional semiconductor memory is increased, it is still limited.
To address these problems, a three-dimensional memory device having a plurality of three-dimensionally arranged memory cells is suggested. However, in order for mass production of a three-dimensional semiconductor memory device, process technologies, which may reduce manufacturing cost per bit to less than that of a two-dimensional semiconductor memory device and realize reliable product characteristics, are required.